Several verification strategies exist to identify unexpected behaviours due to the presence of bugs in system-level HW/SW descriptions. However, when the bug is found, further effort must be spent by the design team to understand its cause and then fix the originating error. This requires a tedious and time-consuming process, generally based on the manual inspection of the execution traces of the design under verification (DUV). This process becomes even more demanding for systems whose behaviours span across wide time windows. Nevertheless, in these cases, usually only a few instructions belonging to long execution traces are relevant for understanding the cause of the unexpected behaviour. Then, we propose a tool that supports the verification engineers in the identification of such a few instructions, to focus their attention on the actual origin of the bug. The tool works by combining dynamic program slicing with a clustering procedure on the execution traces corresponding to unexpected behaviours. Firstly, program slicing is applied to remove instructions not belonging to the cone of influence of the unexpected behaviour. Then, clusters of instructions based on store operations at the LLVM intermediate representation of the DUV are created to guide the heuristic in removing further irrelevant instructions.